In a conventional household washing machine which has a centrifugal extractor, a spin basket is made of metal and metal or concrete is used as a balancing weight. The weight of the structure becomes fairly high because it totals 13 kg from the 8 kg of the spin basket to which is added the 5 kg of the balancing weight. If a spin basket made of plastic is used, the weight of the structure becomes lighter because the spin basket weighs only 2 kg. However, deformation and vibration of a spin basket made of plastic tends to become large at the beginning of rotation and during synchronous rotation of the basket. It is impossible to make the weight of the entire structure small because it is necessary to increase the weight of the balancing weight to 11 kg in order to satisfy the balancing function due to the small weight of the plastic spin basket.
Therefore, it is considered to make a spin basket of plastic and use a balancing ring which consists of a hollow ring containing liquid as the balancing weight.
A conventional balancing ring is described as follows with reference to FIGS. 1 and 2.
Numeral 1 indicates a cabinet and 2 indicates a plastic spin basket which holds a washing basket which is suitably mounted in said cabinet 1. A rotary agitator 3 is provided at the bottom of said spin basket 2. A water tank 4 is supported by a plurality of supporting means 5. Numeral 6 indicates a driving motor for the spin basket 2 and rotary agitator 3 provided at the bottom of the water tank 4. A bearing 7 is provided for the spin basket 2 and the rotary agitator 3. Numeral 8 indicates an upper cover for the washing machine and 9 indicates a control box. A balancing ring 10 is attached to the side wall of the spin basket 2. As shown in FIG. 2, the balancing ring 10 consists of a hollow ring 11 which is provided with a plurality of projecting partition boards 16 mounted on the lower wall. The ring 10 is filled approximately one-half full of water 17.
The space 14 between a said partition board 16 and the inside wall 12 of the hollow ring 11 is made large in order that the water 17 may flow easily thereby supplementing the unbalance of the mass of clothes in the spin basket 2 at the beginning of rotation. The space 15 between a said partition board 16 and the outside wall 13 of said hollow ring 11 is made small in order to prevent the occurrence of abnormal vibration of the spin basket 2 by violent flowing of water which is moved to the vicinity of said outside wall 13 by the centrifugal force produced by the increase of rotational speed of the basket.
In this conventional balancing ring, however, if said partition board 16 is made large in order to suppress the flow of water, the balancing action of the water is delayed and abnormal vibration occurs because rapid flow of said water is prevented by the resistance of the large area of the partition board 16 at the beginning of rotation of the spin basket 2. Conversely, if the partition board 16 is made small, it is effective for the water to hold balance because the water can flow easily at the beginning of rotation. However, from the time of passing the critical speed after the start of rotation to the time of synchronous rotation, water moved to the vicinity of said outside wall 13 begins to flow violently above the partition board 16, and abnormal vibration of the basket occurs since it is out of balance. This describes the problem in the conventional balancing ring.